The problem of erosive damage to seals and metal components in downhole flow devices has been a challenge in the industry for quite some time. In a wellbore, for example, sliding sleeves are used in applications where high velocity flow can create a very hostile environment. The high velocity flow, especially when it contains solids, can induce flow erosion even in the hardest materials available. Additionally, when a pressure differential is unloaded across a conventional seal, severe damage can occur that renders the seal inoperable.
In the prior art, techniques that address unloading of a pressure differential across seals have used thin equalizing slots and diffuser type seals. The arrangement is intended to prevent damage to two sets of seals, or packing units, that create a barrier between the annulus and tubing pressure. Examples of this prior art technique are disclosed in U.S. Pat. Nos. 5,316,084 and 5,156,220. Prior designs such as these may not prevent damage to seals caused by abrasive flow because the seals may never be adequately protected from an initial surge of pressure during the opening sequence.
Although prior art sealing techniques may be effective, operators are continually striving for improvements to reduce the effects of erosion or pressure differential on seals used downhole. Accordingly, the subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.